Abstract Four economic porphyry Cu–Au deposits and several prospects have been investigated in the Northparkes district, part of the Ordovician to early Silurian Junee–Narromine Belt of the Macquarie Arc, New whole-rock geochemical data from the Northparkes porphyry Cu–Au district, NSW, indicate that the mineralising intrusive complexes exhibit distinct arc signatures that are transitional from high-K calc-alkaline to silica-saturated alkalic. Based on ratios of Sr/Y vs Y (e.g. Sr/Y > ∼20 and Y < ∼17 ppm) the mineralising intrusions are interpreted to have crystallised from fractionated hydrous melts indicating the suppression of plagioclase crystallisation in favour of hydrous mineral phases. This interpretation is supported by listric-shaped rare earth element curves and the presence of primary hornblende phenocrysts indicating elevated magmatic water contents. There is an association of mineralising intrusions with a low Zr trend both in the mineralised Northparkes district intrusive rocks and in mineralised porphyry-related intrusive rocks globally. A newly developed fertility indicator ratio Zr/Y ∼10% is more accurate at identifying the mineralised rocks at Northparkes than the conventional Sr/Y vs Y fertility indicator diagram, successfully identifying 92% of the mineralising intrusions, mainly owing to the fact that it is less affected by hydrothermal alteration. The insensitivity of Zr–Y to alteration makes this indicator a useful new tool that may lead to enhanced probabilities for future discoveries in the Northparkes district, broader Macquarie Arc and altered rocks globally. KEY POINTS Mineralising intrusions in the Northparkes district have distinct Zr vs Y concentrations. The Zr vs Y indicator of magmatic fertility is less sensitive to alteration than Sr-based indicators. The Zr vs Y magmatic fertility indicator identified at Northparkes is not unique and identifies mineralising intrusions in other porphyry fields.

中文翻译：

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Northparkes 区的斑岩肥力：来自全岩地球化学的指标

摘要 北帕克斯区是麦格理弧的奥陶纪至早志留世 Junee-Narromine 带的一部分，在北帕克斯区调查了四个经济斑岩铜金矿床和几个前景，来自北帕克斯斑岩铜金区的新全岩地球化学数据， NSW，表明矿化侵入复合体表现出明显的弧特征，从高 K 钙碱性过渡到二氧化硅饱和碱性。根据 Sr/Y 与 Y 的比率（例如 Sr/Y > ～ 20 和 Y < ～ 17 ppm），矿化侵入体被解释为从分馏的含水熔体中结晶，表明斜长石结晶的抑制有利于含水矿物相。这一解释得到了李斯特形稀土元素曲线和表明岩浆含水量升高的原始角闪石斑晶的存在的支持。在全球的矿化 Northparkes 区侵入岩和矿化斑岩相关侵入岩中，矿化侵入体与低 Zr 趋势有关。新开发的肥力指标比 Zr/Y ∼10% 在识别 Northparkes 矿化岩方面比传统的 Sr/Y vs Y 肥力指标图更准确，成功识别了 92% 的矿化侵入体，主要是因为它受热液蚀变影响较小。Zr-Y 对蚀变的不敏感性使该指标成为有用的新工具，可能会导致未来在 Northparkes 地区、更广泛的 Macquarie Arc 和全球蚀变岩石中发现的可能性增加。要点 北帕克斯区的矿化侵入体具有明显的 Zr 与 Y 浓度。岩浆肥力的 Zr vs Y 指标对蚀变的敏感度低于基于 Sr 的指标。在 Northparkes 确定的 Zr 与 Y 岩浆肥力指标不是唯一的，它确定了其他斑岩领域的矿化侵入体。